1. Field of the Invention
The present invention relates generally to a liquid crystal display device, and more particularly to a liquid crystal display device which is configured to have a pair of electrodes on one of substrates that constitute a liquid crystal display panel, the pair of electrodes being opposed to each other via an interlayer insulation film.
2. Description of the Related Art
In recent years, flat-panel display devices have vigorously been developed, and liquid crystal display devices, above all, have attracted attention because of advantages of light weight, small thickness and low power consumption. In particular, in an active matrix liquid crystal display device in which a switching element is built in each of pixels, attention has been paid to the structure which mainly makes use of a transverse electric field (including a fringe electric field) of an IPS (In-Plane Switching) mode or an FFS (Fringe Field Switching) mode (see, e.g. Jpn. Pat. Appln. KOKAI Publication No. 2005-107535 and Jpn. Pat. Appln. KOKAI Publication No. 2006-139295).
The liquid crystal display device of the IPS mode or FFS mode includes a pixel electrode and a common electrode which are formed on an array substrate, and liquid crystal molecules are switched by a transverse electric field that is substantially parallel to the major surface of the array substrate. In addition, polarizer plates, which are disposed such that their axes of polarization intersect at right angles, are disposed on the outer surfaces of the array substrate and a counter-substrate. By this disposition of the polarizer plates, a black screen is displayed, for example, at a time of non-application of voltage. With the application of a voltage corresponding to a video signal to the pixel electrode, the light transmittance (modulation ratio) gradually increases and a white screen is displayed. In this liquid crystal display device, since the liquid crystal molecules rotate in a plane that is substantially parallel to the major surface of the substrate, the polarization state is not greatly influenced by the incidence direction of transmissive light. Hence, the viewing angle dependency is small, and wide viewing-angle characteristics are obtained.
Jpn. Pat. Appln. KOKAI Publication No. 2000-047250, for instance, discloses a technique for solving such a problem that a display image in an IPS system is influenced by an electric field which occurs due to a variation in potential of a signal line after data write in pixels, or an electric field which occurs due to a variation in potential of neighboring signal lines. According to this technique, a wide pixel section area is secured by sharing a signal line and a pixel electrode, without disposing wiring for preventing this influence.
Jpn. Pat. Appln. KOKAI Publication No. 2001-174784, for instance, discloses a technique for preventing a potential variation from occurring in a pixel voltage of each pixel when a voltage, which is applied to each scanning signal line, has changed from a select scan voltage to a non-select scan voltage. In particular, as regards an IPS system liquid crystal display module, this document discloses a technique for decreasing a maximum amplitude level of a gradation voltage which is applied to a pixel electrode.
In a liquid crystal mode which mainly makes use of a transverse electric field, it is desired to shield an electric field from a signal line, which adversely affects a display image, and to suppress an unwanted parasitic capacitance, thereby improving display quality.